ICU-22721 Prevent redundant concurrent CI runs on the same PR branch

.ci-builds/.azure-exhaustive-tests.yml

@@ -7,6 +7,10 @@
 # also batch up any pending changes so that we will only have at most
 # one build running at a given time (since they take a long time).
 trigger:
+  # batch=true to reduce number of concurrent runs on the same branch:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/yaml-schema/trigger?view=azure-pipelines#properties
+  # potential future feature to supersede batch=true:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/process/stages?view=azure-devops&tabs=yaml#specify-queuing-policies
   batch: true
   branches:
     include:

.ci-builds/.azure-pipelines-icu4c.yml

@@ -1,6 +1,11 @@
 # Azure Pipelines (VSTS) configuration for CI builds for ICU.
 
 trigger:
+  # batch=true to reduce number of concurrent runs on the same branch:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/yaml-schema/trigger?view=azure-pipelines#properties
+  # potential future feature to supersede batch=true:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/process/stages?view=azure-devops&tabs=yaml#specify-queuing-policies
+  batch: true
   branches:
     include:
     - main

.ci-builds/.azure-pipelines-icu4j.yml

@@ -1,6 +1,11 @@
 # Azure Pipelines (VSTS) configuration for CI builds for ICU.
 
 trigger:
+  # batch=true to reduce number of concurrent runs on the same branch:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/yaml-schema/trigger?view=azure-pipelines#properties
+  # potential future feature to supersede batch=true:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/process/stages?view=azure-devops&tabs=yaml#specify-queuing-policies
+  batch: true
   branches:
     include:
     - main

.ci-builds/.azure-post-merge-tests.yml

@@ -1,5 +1,10 @@
 # Azure Pipelines (VSTS) configuration for testing things post merging
 trigger:
+  # batch=true to reduce number of concurrent runs on the same branch:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/yaml-schema/trigger?view=azure-pipelines#properties
+  # potential future feature to supersede batch=true:
+  # https://learn.microsoft.com/en-us/azure/devops/pipelines/process/stages?view=azure-devops&tabs=yaml#specify-queuing-policies
+  batch: true
   branches:
     include:
     - main

.github/workflows/icu4c.yml

@@ -22,6 +22,13 @@ on:
     # To trigger the Env Test workflow manually, follow the instructions in
     # https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 permissions:
   contents: read
 

.github/workflows/icu4j.yml

@@ -22,6 +22,13 @@ on:
     # To trigger the Env Test workflow manually, follow the instructions in
     # https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 env:
   SHARED_MVN_ARGS: '--show-version --no-transfer-progress'
 

.github/workflows/icu_common.yml

@@ -16,6 +16,13 @@ on:
     # To trigger the Env Test workflow manually, follow the instructions in
     # https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 env:
   SHARED_MVN_ARGS: '--show-version --no-transfer-progress'
 

.github/workflows/icu_docs.yml

@@ -22,6 +22,13 @@ on:
     # To trigger the Env Test workflow manually, follow the instructions in
     # https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 permissions:
   contents: read
 

.github/workflows/icu_merge_ci.yml

@@ -14,6 +14,13 @@ on:
     # To trigger the Env Test workflow manually, follow the instructions in
     # https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 env:
   SHARED_MVN_ARGS: '--show-version --no-transfer-progress'
 

.github/workflows/icu_valgrind.yml

@@ -20,6 +20,13 @@ on:
       - 'icu4c/**'
       - '.github/workflows/**'
 
+# For non-release branches (namely: PRs), only run CI on the most recent commit. Cancel
+# runs on previous commits mid-flight when new commits are pushed.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-only-cancel-in-progress-jobs-on-specific-branches
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'maint/') && github.ref != 'main' }}
+
 permissions:
   contents: read